diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/bug649939.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/bug649939.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,27 @@
+// This was the actual bug
+assertRaises(StopIteration, function() {
+    Iterator.prototype.next();
+    Iterator.prototype.next();
+});
+
+// The error should have triggered here, but was masked by a latent bug
+assertRaises(StopIteration, function() {
+    Iterator.prototype.next();
+});
+
+// Found by fuzzing
+assertRaises(StopIteration, function() {
+    (new Iterator({})).__proto__.next();
+});
+
+
+function assertRaises(exc, callback) {
+    var caught = false;
+    try {
+        callback();
+    } catch (e) {
+        assertEq(e instanceof StopIteration, true);
+        caught = true;
+    }
+    assertEq(caught, true);
+}